Numerous types of nonwoven disposable absorbent articles are commercially available, and are manufactured for use in the absorption and containment of bodily waste such as urine and feces. Typical of such articles are disposable diapers for infants, and undergarments for incontinent adults. In the construction of such disposable articles, an inner leg gather or cuff is employed to prevent leakage of the bodily waste around the user's legs. During use, this cuff or flap is held in place with one or more elastic bands surrounding the leg. These elastic bands are typically held in place and attached to the disposable article by a hot melt adhesive.
While a wide range of hot melt adhesive compositions are known and used in the construction of disposable articles, it is also well known that a hot melt adhesive used for bonding in a particular use or application may be completely unsuitable for other uses or applications. Thus, various hot melt adhesive compositions are used in the construction of disposable articles. For example, it is well known that polyolefin-based hot melt adhesives are suitable for the construction of diapers, particularly in the bonding of polyethylene films, or the like, to issue or nonwoven substrates in the production of such articles. However, it is also known that most polyolefin-based hot melt adhesives are not suitable for bonding of the elastic bands in the diapers because their creep resistance is insufficient for such an application. For this reason, hot melt adhesives such as styrene-isoprene-styrene (SIS) block copolymers or styrene-butadiene-styrene (SBS) block copolymers are used.
These block copolymers, however, lose most of their bond strength upon exposure to oil-based emollients. Mineral oil and other oil-based ointments or lotions, referred to herein as emollients, are often rubbed on the skin of infants by the caregiver to treat and/or prevent skin rashes. Emollients may also be applied to or pre-coated on the non-woven skin-contacting layer of diapers and other absorbent articles by the manufacturers of such articles. It is believed that emollients disturb the bond of adhesives by two mechanisms. First, they migrate into the adhesive-substrate interface and thereby disrupt the bond. Second, the emollient is absorbed into and plasticizes the adhesive which reduces the cohesive strength of the adhesive. Thus, prior hot melt adhesive compositions, upon exposure thereto, experience adhesive bond failure. As a result, the elastic leg bands may actually let loose from the diaper resulting in complete failure and break down of the inner leg cuff. Also, construction adhesives may fail resulting in undesirable delamination of the absorbent article. Therefore, an adhesive that is capable of withstanding exposure to emollients while still providing sufficient bond strength would be highly desirable.